Abstract
We examined changes in selected muscle performance parameters after 8 weeks of interval training using two opposite running inclinations. We hypothesized that the uphill training will affect endurance muscle performance outcomes, whereas the downhill training will affect power muscle performance outcomes. Fourteen physically active volunteers were randomly assigned into either the Uphill group (UG; n = 7; uphill interval running at +10% incline) or the Downhill group (DG; n = 7; downhill interval running at −10% incline) and completed 16 training sessions. Each session consisted of ten 30 s treadmill runs at 90% of maximum aerobic speed (MAS) with a work to rest ratio of 1:2. Vertical jump performance, isometric (MVC) and isokinetic torque of knee extensors and flexors, and fatigue of knee extensors were evaluated pre and post‐training. Moreover, body composition (via bioimpedance) and vastus lateralis muscle architecture (via ultrasonography) were assessed pre and post‐training. Relative lean tissue mass, relative fat mass, and squat jump (cm) significantly (p < .05) changed from baseline values by +4.5 ± 4.0%, −11.5 ± 9.6%, and +9.5 ± 11.7%, respectively, only in the DG. Similarly, DG improved absolute values of knee extension rate of torque development and impulse (p < .05), whereas knee flexion peak torque angle significantly decreased in both groups (p < .05). On the other hand, the UG increased the number of repetitions achieved during the fatigue protocol and total work by 21.2 ± 32.6% and 13.8 ± 21.2%, respectively (p < .05). No differences were found between groups in muscle architecture. Introducing variations in slope during HIIT could be used to induce specific improvements toward muscle endurance or power performance characteristics.
Highlights
High-intensity interval training (HIIT) has emerged as an effective method for improving performance in elite or recreational athletes, in addition to offering health-related fitness benefits (Gibala et al, 2012)
HIIT involves speeds ranging from 80% to 100% of Maximum Aerobic Speed (MAS) (Bartlett et al, 2012) up to maximal sprinting speed (Willoughby et al, 2016), allowing for a number of repetitions to be completed with brief recovery intervals (Buchheit & Laursen, 2013) and permits an effective use of training time
The mid-training evaluation of maximum aerobic speed (MAS) resulted in the re-adjustment of running speed for five subjects from the Uphill group (UG) and for six subjects from the Downhill group (DG)
Summary
High-intensity interval training (HIIT) has emerged as an effective method for improving performance in elite or recreational athletes, in addition to offering health-related fitness benefits (Gibala et al, 2012). Running on a positive slope (uphill) provides a “resistance” against the gravitational pull on the runner's body but the potential benefits on muscle power are not yet clear (Ferley et al, 2014). In well-trained female and male distance runners performing two high-intensity interval sessions and two continuous run sessions per week, uphill running was found to improve running economy, but not muscular power (Ferley et al, 2014). Another study employing variable slopes (up to 30% positive grade) and running speeds up to maximum for 6 weeks, revealed that uphill running can be as effective as resistance training in improving sprint start speed (Myer et al, 2007). It has been shown that combining eccentric resistance training with downhill running provided greater improvements in peak power of the countermovement jump (CMJ) and improved maximal running speed, compared to eccentric resistance alone or traditional resistance training (Cook et al, 2013)
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